Unloading and capacity-regulating mechanism for compressors.



B. V. NORDBERG, UNLOADING AND CAPACITY REGULATING MECHANISM FOR cowmssorrs.

, APPLICATION FILED APR-16, 19M. mawm Patentedfiept. 11,1917.

2 SHEETS-SHEET l.

Fga Z,

Ivar/126M607":

. @M fi Wm W P ZXZW B. Vi NORDBERG.

UNLOADING AND CAPACITY REGULATING mscx-mmsm FOR comwmssons. n APPLICATION FILED APR. 6| I914. J 1 J I 1 Q@@,9{6D Pwaemed H, 19%,

2 SHEETSSHEET 2.

BRUNO v. nonnsnne, or MILWAUKEE, WISCONSIN.

UNLOADIING AND CAPACITY-REGULATING MECHANISM FOR COMPRESSOR-S.

Specification of Letters Patent.

Patented Sept. till, 1911?.

Application filed April 16, 1914. Serial No. 832,191.

To all whom it may concern:

Be it known that I, BRUNO V. NoRDBERe,

a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented certain new and useful Improvements in Unloading and Capacity-Regulating Mechanism for Compressors, of which the following is a specification, reference being had to the accompanying drawing, forming a thereof.

This invention relates to compressors which are designed to run at a substantially constant speed and upon which the demand is variable.

Its main object is to automatically maintain a substantially, constant discharge pressure independently of the speed of the compressor, to provide against accidents resultingfrom dangerously high pressure when the demand on the compressorceases or is suddenly or materially reduced, and generally to improve the construction and operation of compressors of this class.

It consists in the-construction, arrangement and combination ofparts as hereinafter particularly described and pointed out in the claims.

Inl the accompanying drawing like characters designate the same parts -in both figures. p

Figure 1 is a side view partly in elevation and partly in section of mechanism embodying the invention as applied to a two-stage compressor; and Fig. 2 is a view partly in elevation and partly in section of a modified arrangement of the mechanism for a duplex single stage compressor.

Referring to Fig. 1, a and b designate the low and high pressure cylinders of a twostage compressor. The cylinders are pro vided at each end, as shown at the left, with automatic or self-acting discharge valves o,

part

operated by an eccentric on the crank shaft of the compressor or other device actuated by the compressor engine through the following mechanism:

An arm 7, provided with a trip steel or block 9, is fixed on the stem h of each valve. At the end opposite the trip steel this aim has a projection 2', which by engagement with a stop j, as shown at the left end of the high pressure cylinder 6. limits the movement of the inlet valved in its wide open position, as shown at the left end of the low pressure cylinder a. An oscillatory lever is, loosely fulcrumed or pivoted on the valve bonnet or stem concentrically with the stem, has one arm connected as indicated, with a wrist plate, eccentric or other actuating device, in the usual or any suitable manner. ()n the other arm of the lever 7c is pivoted a latch Z, provided with a trip steel or block m, adapted by engagement with the trip block or steel 9 on the arm f to close the inlet valve (Z when the lever moves in the direction indicated by the arrow at the right end of the low pressure cylinder. The

latch is formed with a heel or shoulder n, e

which extends further toward the valve stem than the trip steel m, and which in any position of the latch is adapted by engagement with the arm to open the valve (Z when the lever 70 moves in a direction opposite to that indicated by the arrow at the right end of cylinder a.

As thus far described, the mechanism is like or similar to Corliss valve gear used on steam engines.

For unloading and for varying and regulating the capacity of a compressor according to the present invention, as the demand on the compressor varies, the following mechanismfor shifting the latches Z into and out of operative position for closing the inder a, to engage with the trip steel 9 on the armf for closing the valve (Z, is in axial alinement with the valve stem h. The arm 0 is connected'by the pin p with a rod 9 extending downwardly into a trip or releas ing cylinder or chamber 1'. As shown in connection with the high pressure cylinder 6, each cylinder 1" is provided with a plunger or movable part s, in engagement with which the rod 9 is held by a spring t phere through an opening around the rod 9,

or above the upper position of the plunger s, so that the plunger is always subjected on the upper side to atmospheric pressure. At the upper limit of the movement of the plunger 8, as shown at the left end of the high pressure cylinder 6, it is held by fluid pressure below it against a beveled seat in the cylinder, thereby preventing the leakage of the fluid pressure medium from the lower part of the cylinder past the plunger to the atmosphere when the latch Z is shifted into inoperative position for closing the valve d Each of the four suction or inlet valves (2 of the cylinders a and b is provided with like valve operating and releasing mechanism, and each of the cylinders or chambers 1' is connected below the plunger 8 with a source of fluid pressure. In the present case the trip or releasing cylinders r of the low pressure cylinder aare connected at their lower ends by pipes 'uand 1), at differcnt points in its length with a regulating or controlling cylinder or chamber w, which is in turn connected at its lower end by a pipe at with the inter-cooler e. The trip or releasing cylinders 1- of the high pressure cylinder Z) are in like manner connected by pipes u and a with a regulating or controlling cylinder w, which in turn is connected at its lower end by a pipe m with a receiver or reservoir (not shown), into which the high pressure cylinder discharges.

Each cylinder or chamber w is provided with a vertically movable plunger or part y, having a stem a passing through the upper end or head of the cylinder or chamber and provided-with a weight 2. Each weight 2 is or may be provided as shown, with one or more removable sections 3, for the purpose of adjustment and varying the discharge pressures of the two compressor cylinders a and b. Each cylinder or chamber w has an opening 4 at its upper end communicating with the atmosphere, and is provided between its upper end and the plunger y with a spring 5, the compression of whichoffers a gradually increasing resistance to the upward movement of the plunger. A spring 6, between the upper end of each cylinder to and the weight 2, cushions the weight at the limit of the downward movement of the plunger y.

lach plunger y is preferably formed at its lower end with a beveled valve face fitting a corresponding seat in the cylinder 10 above the pressure supply pipe 22, so that when the compressor is working at full capacity,

leakage of compressed air from the high presure receiver or reservoir and from the intercooler to the atmosphere, is prevented,

The arms f of each cylinder are connected with each other by a spring 7., which tends when they are released by the latches Z, to hold the projections 11 in engagement with the stops j and the valves (1 open, as shown at the left of the high pressure cylinder.

In the operation of a two-stage compressor of the type described, when the pressure in the receiver or reservoir into which the high pressure cylinder 6 discharges, rises to a certain point according to the adjustment of the weight by which the plnnger y is loaded, the plunger will be lifted and will first uncover the opening into pipeu, which leads to the releasing cylinder 1' at the left end of the high pressure cylinder 6. Thereupon compressed air admitted into the lower end of the cylinder 1' will lift the plunger 8 and shift the latch Z, as shown, out of operative position to close the associated valve 01. Said valve will thus be left in its open position by the latch Z, as shown at the left end of the low pressure cylinder a, and will be held in such position with the pro'ection 6 against the stop j by the spring 7, thereby unloading the left end of the high pressure cylinder until the latch Z is shifted back into operative position for engagement of the trip steels or blocks 9 and m.

Under normal conditions the unloading of one end of the high pressure cylinder as above stated, will be immediately followed by a slight rise of pressure in the intercooler e. This increase of pressure in the intercooler communicated through the pipe m to the regulating or controlling cylinder '20 of the low pressure cylinder will lift the plunger 3 therein till it uncovers the opening into the pipe at leading to the trip or releasing cylinder 1* at the left end of the low pressure cylinder. Thereupon the latch Z of the valve (5 at that end of the low pressure cylinder, will be shifted out of operative position for engagement with the trip steel or block 9 and said valve will be left and will remain in its open position, as above explained in connection with the valve mechanism at the left end of the high pressure cylinder.

If the demand on the compressor is re duced so that the pressure in the receiver or reservoir into which the high pressure cylinder discharges, continues to rise, the plunger y at theright will belifted above the opening into the pipe 1), thereby admitting compressed air into the lower end of the cylinder 7* at the right end of the high pressure cylinder. Thereupon the valve releasing mechanism will be shifted so as to leave the associated suction valve 03 open and inactive and completely unload the high pressure cylinder. Immediately following this operation, under normal conditions, a further increase of pressure in the intercooler will operate on the plunger y in the regulating or controlling cylinder w at the left, to shift the valvereleasing mechanism at the right end of the low pressure cylinder, and will in like manner leave the suction valve 'at that end of said cylinder open and inactive, thus completely unloading the low pressure cylinder.

As it is of the utmost importance in unloading and regulating the capacity of a compressor of this kind, that the low pres sure cylinder be unloaded whenever the pressure in the intercooler rises to a certain point or points, to avoid the possibility of a dangerousl y high pressure in the intercooler, the valve releasing and. unloading devices of the two cylinders are operated independently of each other, according to changes in the discharge pressures of the high and low pressure cylinders respectively, so that the unloading mechanism of the low pressure cylinder may operate in advance of the operation of the unloading mechanism of the high pressure cylinder in case the pressure in the intercooler, on account of leaky suction or inlet valves in the high pressure cylinder or froni'other causes, rises above predetermined limits in advance of acorresponding rise of pressure in the receiver of reservoir connected with the high pressure cylinder. Under ordinary conditions however, when the valves and valve mechanism of the two cylinders function properly, the unloading mechanism of the low pressure cylinder will operate simultaneously with or immediately following the operation, of the unloading mechanism of the high pressure cylinder.

When the pressure in the receiver or reservoir into which the high pressure cylinder discharges is lowered on account of increased demandon the compressor, the plunger 3 of the regulatingor controlling cylinder to of the high pressure cylinder will be moved downward by the action of the weight 2 and the spring 5, first cutting off the supply of compressed air to the trip or releasing cylinder rat the right, and then if the pressure in the receiver or reservoir continues to fall, cutting off the supply of compressed right end of each cylinder, for closing thevalves d on the working or compression strokes'of the high pressure piston. Simultaneously with or immediately following theshifting of the latches of the high pressure cylinder into operative position for closing the suction or inlet valves d of said cylinder, the latches at the corresponding ends of the low pressure cylinder will be shifted into operative position. Thus the two cylinders are automatically unloaded and loaded, one end at a time, according to variations in the demand upon the compressor and consequent variations in the dis charge pressures of the high and low pressure cylinders respectively, within certain limits.

Referring to Fig. 2, showing a modifi cation of the mechanism as applied to a duplex single stage compressor, in which each end of each cylinder constitutes by itself a compressor, it is desirable to so construct and arrange the unloading mechanism that the compressor may be operated either at full capacity, three-fourths capacity, onehalf capacity, one-fourth capacity or zero capacity. To this end each of the four suction or inlet valves is provided with mechanism like or similar to that shown in Fig. l, and each valve has a tripping or releasing cylinder. The several tripping and releasing cylinders designated 7*, r r' and 9" are connected by pipes 21 with a regulating or controlling cylinder w at different points in the direction of its length, so that in the operation of the mechanism, the several inlet valves will be released and left open when the plunger 3 moves upward and will be brought into action when the plunger moves downward, in succession.

The regulating or controlling plunger 3 might be loaded as shown in Fig. 1, but in some cases it is desirable that as the capacity of the compressor is reduced, the discharge pressure should be increased by predetermined increments. For this purpose the plunger rod a is connected by a link with a lever 8, and the weight by which the plunger is loaded is made in four sections, 2, 2", 2 and 2 The lower and smaller section 2 is attached to a rod 9, which is connectedby a link with the lever 8 and is guided in a holder or casing 10. The other three sections, which increase progressively upward in size or diameter, normally rest when the compressor is operating under normal conditions at full capacity, on shoulders or projections in the holder or casing 10, one above another. The arrangement is such that when the discharge pressure rises sufficiently to lift the plunger 3/ into position as shown, to establish communication between the compressed air or fiuid pressure supply connection 02 and the tripping or releasing cylinder 7- through the pipe at leading to said cylinder, the lower section 2 of the weight will be lifted into engagement with the next section 2 above it. A further increase in the discharge pressure sufficient to lift the plunger 3 into position gagement with the section 2 to establish communication between the pressure supply connection m and the cylinder 1', will lift both sections 2 and 2 till the section 2 engages with the section 2 A still greater increase in the discharge pressure suflicient to lift the three sections 2, 2 and 2 will lift the plunger y into position to establish communication between the pressure supply connection a: and the cylinder 1'" and carry the section 2 into en- Finally, a still greater increase in discharge pressure will lift the four sections and carry the plunger y upward into position to establish communication between the pressure supply connection a: and the last cylinder 1' thereby completely unloading the compressor, all of the tripping or releasing cylinders being connected with the fluid pressure sup ply w and all of the inlet valves released and inactive in open position, as shown at the left on Fig. l.

lVhen the demand on the compressor increases and the discharge pressure falls, the plunger y will descend, due to the action of the sectional weight, and the several tripping or releasing cylinders will be cut ofl from the pressure supply connection 00 and brought into communication with the atmosphere through the opening l, one after another, in the reverse order.

To steady the movement of the unloading mechanism or of the plunger y which controls the same, the lever 8 may be connected with a plunger 11 in a cylinder-12 containing oil or other liquid and provided with a by-pass 13. For a single stage, single cylinder compressor, the unloading mechanism may be constructed and arranged as shown by Fig.1, in connection with either the high or low pressure cylinders.

Various changes in details of construction and arrangement of parts may be made without departing from the principle and scope of the invention as defined in the following claims.

I claim:

1. In a compressor the combination of a cylinder provided with suction ports, positively actuated suction valves adapted to close said ports on the compression strokes of the piston, releasing means comprising chambers having fluid pressure supply connections and movable members adapted when subjected to pressure to render the valve closing means inoperative, fluid pressure controlling means comprising a chamber having a loaded movable part constantly subjected to the discharge pressure of the cylinder and adapted at different points in its traverse coincident with predetermined increases of such pressure to admit fluid pressure to said releasing chambers one after the other and upon corresponding reductions of said discharge pressure to open said retion with a'moving part of the compressor,

a latch pivotally mounted on said lever and adapted by engagement with said arm to close the valve on the compression stroke of the piston; releasing means comprising a,

chamber having a fluid pressure supply connection and a movable member connected with said latch and adapted when subjected to pressure to shift and hold the latch out of operative position in any part of the traverse of said arm; and fluid pressure controlling means comprising a chamber having a loaded movable part constantly subjected to the discharge pressure of the cylinder and adapted when said pressure rises to a certain point to admit fluid pressure to the releasing chamber and when such pressure falls below that point to open said releasing chamber to exhaust.

3. In a compressor the, combination of a cylinder provided with a rotative suction valve; valve operating mechanism comprising an arm fixed on the valve stem, an 0scillatory lever having an actuating connection with a. movable part of the compressor, and a latch pivotally connected with said lever and adapted by engagement with said arm to close said valve on the compression stroke of the piston, said latch being provided with an arm at an angle thereto and with a heel adapted by engagement with the valve arm to open the valve on the suction stroke of the piston; releasing means comprising a chamber having a fluid pressure supply connection and a movable member connected with the latch arm in axial alinement with the valve stem when the latch is in operative position for closing the valve, and adapted when subjected to pressure to shift and hold the latch out of operative position in any part of the traverse of said valve stem arm; and fluid pressure controlling means comprising -a chamber connected with the discharge of saidcylinder and having a loaded movable part constantly subjected to discharge pressure and adapted when such pressure rises to a'certain pointto admit fluid pressure to the releasing chamber, and when such pressure falls below that point to open said releasing chamber to exhaust.

4. In a compressor the combination of a cylinder provided at the ends with rotative suction valves; valve operating mechanism comprising arms fixed on the valve stems, oscillatory levers fulcrumed concentrically with the valve stems and having'an actuating connection with a moving part of the nasaaee compressor, and latches pivotally mounted on said levers and adapted by engagement with said arms to close the valves on the compression strokes of the piston, said latches being provided with arms at an angle thereto and with heels adapted by engagement with the valve arms to open the valves on the suction strokes of'the piston; releas-' ing means comprising fluid pressure cham bers and movable members connected with the latch arms in axial alinement with the valve stems when the latches are in engaging positions for closing the valves, and adapted when subjected to pressure to shift and hold the latches out of operative position for closing the valves; and fluid pressure controlling means comprising a chamber having a loaded movable part constantly subjected to the discharge pressure of the cylinder and, adapted at different points in its traverse coincident with predetermined increases of such pressure to admit fluid pressure to the releasing chambers one after the other, and upon corresponding reductions of said discharge pressure to open said releasing chambers to exhaust in the reverse order.

5. In a compressor the combination of a cylinder provided with a rotative suction valve; valve operating mechanism comprising an arm fixed on the valve stem, a fixed stop in the path of said arm for limiting its movement in the open position of the valve,

a spring connected with said arm and tend--- ing to hold it against said stop, an oscillatory lever having an actuating connection with a moving part of the compressor and fulcrumed coaxially with the valve stem, and a latch pivotally mounted on said lever and adapted by engagement with said arm to, close the valve on the compression stroke of the piston, said latch being provided with an arm at an angle thereto and with a heel adapted in any position of the latch to engage with the valve arm and open the valve on the suction stroke of the piston; releasing means comprising a chamber having a fluid pressure supply connection and a movable member connected with the latch arm in axial alinement with the valve stem when the latch is in engaging position for closing the valve and adapted when subjected to pressure to shift said latch out of operative position for closing the valve in any part of the traverse of said valve stem arm; and fluid pressure controlling means comprising a chamber connected with the discharge of the cylinder and having a loaded movable part constantly subjected to discharge pres sure and adapted when such pressure rises to a certain point to admit fluid pressure to thereleasing chamber and when such pressure falls below that point to open said releasing chamber to exhaust,

6. In a compressor the combination of a cylinder provided at the ends with rotative suction valves; valve operating mechanism comprising arms fixed on the valve stems, fixed stops for limiting the movement of said arms in the open position of the valves, a spring connected with said arms and tending to hold them against said stops, oscillatory levers having an actuating connection with a moving part of the compressor and fulcrumed concentrically with the valve stems, and latches pivotally mounted on said levers and adapted by engagement with said arms to close the valves'on the compression strokes of the piston, said latches being provided with arms at an angle thereto and with heels adapted in anyposition of the latches by engagement with the valve arms to open the valves on the suction strokes of the piston; releasing means comprising chambers having fluid pressure supply connections and movable members connected with the latch arms in axial alinement with the valve stems when the latches are in operative position for opening the valves and adapted when subjected-to pressure to shift the latches out of operative position for closing the valves; and fluid pressure controlling means comprising a chamber having a loaded movable part subjected to the discharge pressure of the cylinder and adapted at difi'erent points in its travel coincident with predetermined increases of such pressure to admit fluid pressure to said releasing chambers one after theother and upon corresponding reductions of said discharge pressure to open said releasing chambers to exhaust in the reverse'order.

7. In a compressor the combination of high and low' pressure cylinders each provided at the ends with suction valves, valve operating mechanism actuated by a'moving part of the compressor and adapted to open said valves on the suction strokes of the piston and to close them on the compression strokes; releasing means comprising chambers having fluid pressure supply connections and movable members adapted when subjected to pressure to render the valve closing means inoperative; fluid pressure controlling means comprising chambers, one communicating with the discharge of the low pressure cylinder and the other with the discharge of the high pressure cylinder and each having a' loaded movable part con-f said releasing chambers to exhaust in the reverse order.

8. In a compressor the combination of a inga chamber having a fluid pressure supply connection and a movable member adapted when subjecting to pressure to render the valve closing means inoperative; and fluid pressure controlling means comprising a chamber communicating with the discharge of said cylinder and having a weighted and spring loaded movable part subjected to the discharge pressure of the cylinder and adapted at different points in its traverse coincident with predetermined increases of such pressure to admit fluid pressure to the releasing chambers, one after the other, and upon corresponding reductions in said discharge pressure to open said releasing chambers to exhaust in the reverse order.

9. In a compressor the combination of a cylinder provided with suction valves; valve operating mechanism adapted to open said valves on the suction strokes of the piston and to close the same on the compression strokes; releasing means comprising a chamber for each of said valves having a fluidpressure supply connection and a movable member adapted when subjected to pressure to render the associated valve closing means inoperative; and fluid pressure controlling means comprising a chamber communicating with the discharge of the cylinder and having an adjustably weighted and spring loaded movable part constantly subjected to the discharge pressure of the cylinder and adapted at different points in its traverse coincident with predetermined increases of such pressure to admit fluid pressure to the releasingchambers one after the other and upon corresponding reductions in said discharge pressure to open said releasing chambers to exhaust in the reverse order.

10. In a compressor the combination of a cylinder provided with suction valves; valve operating mechanism adapted to open said valves on the suction strokes of the piston and to close the same on the compression strokes; releasing means comprising chambers having movable members adapted when subjected to pressure to render the valve closing means inoperative; and fluid pressure controlling means comprising a cylinder communicating with the discharge of the compressor and connected at different points in the direction of its length with said releasing chambers, and a loaded plunger fitted in said controlling cylinder and adapted when subjected to 'certain increases in the discharge pressure to establish communication between said controlling cylinder and the releasing chambers one after the other, and upon corresponding reductions in such pressure to cut oil the supply of fluid pressure to the releasing chambers and open them to exhaust in the reverse order.

In witness whereof I hereto aflix my sig nature in presence of two witnesses.

BRUNO V NORDBERG. Witnesses:

E. G. BAYERLEIN, CHAS. L. Goes. 

